1. Field
The present disclosure relates to batteries, and more particularly pertains to a new system for reducing thermal transfer between cells in a battery to reduce the possibility of a cascade thermal runaway of cells in the battery.
2. Description of the Prior Art
The use of portable devices for various tasks has become ubiquitous, and while the miniaturization of various components that make up these devices is a part of their increasing popularity, and the ability to power these devices for longer and longer time periods has also added to the portability and ease of use of the devices. Contributing to the improvement in the ability to power these portable devices is the development of new battery technologies with seemingly ever increasing charge capacities in smaller and smaller packages.
These developments have not been without their occasional drawbacks, and one example of this is the development of lithium ion battery technology. While delivering relatively greater charge capacities in relatively smaller packages, the lithium ion cells have the potential to generate very high temperatures if there is a failure in the circuitry or structure of the cell that causes, for example, a short circuit. These high temperatures are not only damaging to the battery and the device in which the lithium ion cell is incorporated or attached, but can cause other damage by fire if the battery continues to malfunction.
More specifically, the effort to increase the density of the cells to provide a greater charge capacity in a smaller space has tended to make the cells more vulnerable to defects and damage that can cause such failures. The increasing density has been achieved through manufacturing techniques that make the components of the cell thinner, such as the separator between anode and cathode. Thus, the manufacturing methods have become more critical not only to the operation of the cell but also to the safety of the cell, especially as the cells become denser. For example, the presence of small metallic dust particles in the cell can cause a short circuit in the cell if these particles come into contact with the oppositely charged parts of the cell. Elimination of all of these dust particles from the manufacturing process may be virtually impossible.
While a mild short may generate only a small amount of heat and may lead to an accelerated degree of self-discharge, the presence of enough metal particles at one location can produce a major electrical short and a much larger current flow between the positive and negative plates, causing a more significant temperature rise and possibly the condition sometimes referred to as “thermal runaway” in which flaming gases may be vented from the cell.
During thermal runaway of a cell, the heat generated in the malfunctioning cell can be transferred to an adjacent cell in the battery package, causing the adjacent cell to become thermally unstable. This heat transfer can lead to a chain reaction in which failure of a cell cascades to an adjacent cell, and the process may be repeated to other cells. Thus, not only can the malfunctioning cell of the battery be affected, but cells adjacent to the malfunctioning cell can be exposed to the heat generated by the malfunction and the performance and operation of the adjacent cell can be affected, even to the point that the adjacent cells can be caused to also malfunction. Typically, a cell will include a vent that allows the hot gases to escape from the interior of a cell when pressures in the interior of the cell exceed a threshold level. The vent is typically located toward or on the end of the cell, which often has an elongated cylindrical shape. The positioning of the vent are the end of the cell, which is often next to an adjacent cell, can allow the hot, pressurized gases escaping from the malfunctioning cell to contact, and heat, the adjacent cell, which can in turn cause overheating and excess pressure in the adjacent cell.
It is therefore believed that there is a need in the art for a device that increases the safety of operation of cells in a battery, especially but not limited to lithium ion batteries, to decrease the possibility that a malfunction in one cell of the battery is able to propagate to another adjacent cell.